Phylum Gnathostomulida Ax, 1956 - gnathostomulids Order Bursovaginoidea Sterrer, 1972 Suborder Scleroperalia Sterrer, 1972 Family Onychognathiidae Sterrer, 1972 Genus Nanognathia Sterrer, 1973 Genus Onychognathia Riedl, 1971 Genus Valvognathia Kristensen & Nørrevang, 1978